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Formication

Formication
Classification and external resources
ICD-10 R20.2
ICD-9-CM 782.0
DiseasesDB 24182
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Formication is the medical term for a sensation that exactly resembles that of small insects crawling on (or under) the skin. It is one specific form of a set of sensations known as paresthesias, which also include the more common prickling, tingling sensation known as "pins and needles". Formication is a well documented symptom, which has numerous possible causes. The word is derived from formica, the Latin word for ant.

Formication may sometimes be experienced as feelings of itchiness, tingling, pins and needles, burning, or even pain. When formication is perceived as itchiness, it may trigger the scratch reflex, and because of this, some people who are suffering from the sensation are at risk of causing skin damage through excessive scratching.

In some instances, static electricity can attract particulates to the skin and can also cause body hair to move, giving a sensation like insects crawling over the skin. However, in many cases no external trigger creates the sensation.

In rare cases, individuals become convinced that the sensation they are suffering is due to the presence of real insects on or under the skin. In these cases, patients have what is known as delusional parasitosis. They believe that their skin is inhabited by, or under attack by, small insects or similar parasites, despite repeated reassurances from physicians, pest control experts, and entomologists.

Causes of formication include normal states such as onset of menopause (i.e. hormone withdrawal). Other causes are medical conditions such as pesticide exposure,mercury poisoning, diabetic neuropathy, skin cancer, syphilis, Lyme disease or herpes zoster (shingles). Formication can be a result of stimulant intoxication (e.g. methamphetamines, cocaine) or alcohol withdrawal in alcoholics (i.e. delirium tremens), and is often accompanied by visual hallucinations of insects (formicanopia). It can also occur as a symptom of benzodiazepine withdrawal and as a side effect of opioid analgesics.


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